IL-12-mediated increases in protection elicited by pneumococcal and meningococcal conjugate vaccines

Interleukin-12 (IL-12) may be a beneficial adjuvant for augmenting vaccine efficacy against encapsulated bacteria such as Streptococcus pneumoniae and Neisseria meningitidis since it can stimulate production of interferon-gam ma (IFN-gamma) and secretion of antibody isotypes that are efficient at med iating complement fixation and opsonophagocytosis. In this study, we demons trate the ability of IL-12 to enhance murine antibody responses, particular ly IgG2a levels, to both pneumococcal and meningococcal conjugate vaccines. Transfer of immune serum from mice immunized with the meningococcal conjug ate vaccine and IL-12 resulted in increased survival times, whereas transfe r of serum from mice immunized with the pneumococcal conjugate and IL-12 re sulted in protection from death upon bacterial challenge. Although treatmen t with vaccine and IL-12 increased levels of IFN-gamma mRNA, IL-12-mediated enhancement of antibody responses still occurred in IFN-gamma - - mice. Th e results demonstrate the effectiveness of IL-12 as an adjuvant for polysac charide conjugate vaccines, especially the pneumococcal conjugate vaccine. (C) 2001 Elsevier Science Ltd. All rights reserved.